code: def test_factor(self):
      key = "img"
      stats = IntensityStatsd(keys=key, ops="max", key_prefix="orig")
      shifter = ShiftIntensityd(
          keys=[key], offset=1.0, factor_key=["orig_max"]
      )
      data = {key: self.imt, PostFix.meta(key): {"affine": None}}
  
      result = shifter(stats(data))
      expected = self.imt + 1.0 * np.nanmax(self.imt)
      np.testing.assert_allclose(result[key], expected)
  
file_path: MONAI/tests/test_shift_intensityd.py
imports: from __future__ import annotations
  import unittest
  import numpy
  from monai.transforms import IntensityStatsd, ShiftIntensityd
  from monai.utils.enums import PostFix
  from tests.utils import TEST_NDARRAYS, NumpyImageTestCase2D, assert_allclose
label_desc: Use image node_id 2 for calling the TestShiftIntensityd obj's underlying member method code with example usage: obj.test_factor() without return types